Rotary mechanical latch
A rotary mechanical latch for positive latching and unlatching of a rotary device with a latchable rotating assembly having a latching gear that can be driven to latched and unlatched states by a drive mechanism such as an electric motor. A cam arm affixed to the latching gear interfaces with leading and trailing latch cams affixed to a flange within the drive mechanism. The interaction of the cam arm with leading and trailing latch cams prevents rotation of the rotating assembly by external forces such as those due to vibration or tampering.
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This application claims the benefit of U.S. Provisional Application No. 61/139,044 filed on Dec. 19, 2008, the entirety of which is herein incorporated by reference.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENTThe United States Government has certain rights in this invention pursuant to Department of Energy Contract No. DE-AC04-94AL85000 with Sandia Corporation.
FIELD OF THE INVENTIONThe invention generally relates to apparatus and methods for a rotary mechanical latching mechanism to provide positive latching of a rotary device. The invention further relates to rotary latching mechanisms for enclosures that are operable by electrical drive means and are resistant to false unlatchings in a vibrational environment.
BACKGROUND OF THE INVENTIONRotary latching mechanisms are used to provide controlled access to enclosures with examples ranging from electronics enclosures, vehicle compartments, control rooms etc. Typically a rotary mechanical latch finds application in locking mechanisms for securing the access panels, doors, lids and hatches to an interior volume of a controlled space. In one exemplary non-limiting application, the knob of a door acts as a driving device for applying torque to a rotating shaft that is coupled to a bolt mechanism for withdrawing the bolt from a corresponding strike plate located on the frame of the door. In this and other applications of rotary latching mechanisms, there is a need to prevent rotation of actuating shaft by unauthorized users and a further need to provide the drive input from a remote location (e.g. by electrical drive apparatus). Additionally there is a need for rotary latching mechanisms that provide positive latching of the actuating shaft in an unpowered state (e.g. passive latching) and are resistant to false unlatching of the actuating shaft due to vibrations in the environment of the latch. The present invention meets these needs by providing a positive rotary latching mechanism that is unlatchable by application of a drive torque to lock and unlock a cam arm attached to a rotary actuation shaft, where the cam arm is latched and unlatched by the cooperative positioning of leading and trailing cams incorporated into the drive mechanism.
The accompanying drawings, which are incorporated in and form part of the specification, illustrate several embodiments of the present invention and, together with the description, serve to explain the principles of the invention. The drawings provided herein are not drawn to scale.
The latchable assembly 140 comprises a latching gear 146, cam arm 148 and a spring catchment 150 that can (as shown in this example) be implemented as a notch on the perimeter of spool 152. The spring catchment 150 can be arranged to capture the free end of a flexural member 158 that as described below, can be configured to apply a latching torque (e.g. via the restoring force of a deformed elastic member) to the latching assembly 140 under certain conditions. The cam arm 148, latching gear 146 and catchment spool 152 fixedly share the axis of rotation 142 and can be assembled onto the output shaft 144 as separate components or can exist as integrally formed or machined components as an application warrants. Latching gear 146 comprises an untoothed portion 156 and a toothed portion 154, the teeth of which are engaged by the teeth of pinion gear 116 during latching and unlatching operations of the rotary latch 100.
In
In an exemplary application, the drive assembly 110 and the latchable assembly 140 can be supported in a common frame or housing, that further can provide an anchor point 160 for the flexible member 158. The free end of the flexible member 158 can slideably engage the recess portion of the spool 152 and can be captured by the spring catchment 150 (e.g. notch or tang) at certain points (described below) during the operation of the rotary mechanical latch 100 to store energy within the flexible member 158 used to produce a latching torque applied to the latching gear 146.
Therefore power is not required to maintain (e.g. latch, lock) the cam arm 148 in the latched state as the curved nature of contacting surfaces 184, 182, 188 and 186 are such as to generate torques (i.e. “restoring” torques) on the flange 118 acting to force engagement of the cam arm 148 with latch cams 120 and 122 in response to any attempt to rotate the cam arm into an unlatched state. In the present exemplary embodiment, it has been found that a useful geometry can be realized with a teardrop leading cam 120, an oblong trailing cam 122 and a cam arm 148 each having contact surfaces (182, 184, 186 and 188) formed to create the opposing torques acting on the flange 118, by the nature of their curvature. It is to be noted that other geometries could be utilized as well without affecting the practice of the present invention (e.g. an elliptical trailing cam in place of the oblong shaped trailing cam). Optional balancing cam 124 has been found useful in applications where the rotary mechanical latch 100 may be subjected to vibrational environments, either due to normal operational conditions or in attempts to defeat the latching device. By balancing the mass distribution of the latching cams 120 and 122 over the flange 118 with a suitable sized balancing cam 124, motion of a drive assembly 110 in response to those vibrations can be minimized. In this embodiment, balancing cam 124 is illustrated as a cylindrical mass attached to the flange 118, but any shaped mass as convenient to an application could be used as well.
The following series of figures serve to explain the operation of the embodiment of a rotary mechanical latch as presented in
The exemplary embodiment of a rotary latch is described in the preceding text as allowing a rotation of the cam arm 148 in an unlatched state through less than 360 degrees. The invention could as well be applied to rotary latches wherein the cam arm 148 was allowed to rotate through a greater rotational angle (i.e. greater than 360 degrees) for example, by providing a rotary ramp element that would move the pinion gear 118 (e.g. or the cam arm itself) out of engagement with the cam arm 148 thereby allowing a greater degree of rotation.
In one exemplary application of the embodiment described above, a rotary mechanical latch has been built and operated with a DC motor drive means (114), and found to cosume 40 millijoules to unlatch. This example serves to illustrate suitability of rotary mechanical latches according to the present invention, to low power applications.
The above described exemplary embodiments present several variants of the invention but do not limit the scope of the invention. Those skilled in the art will appreciate that the present invention can be implemented in other equivalent ways. The actual scope of the invention is intended to be defined in the following claims.
Claims
1. A rotary mechanical latch for positive latching and unlatching of a rotary device, the latch comprising:
- a latchable rotatable assembly having a first axis of rotation including, a latching gear rotatable about the first axis and having a perimeter including a toothed portion and an untoothed portion, a cam arm affixed to the latching gear and rotatable about the first axis, the cam arm having an extension aligned with the untoothed portion of the latching gear, a spring catchment spool affixed to the latching gear and having a perimeter and a spring catchment disposed on the perimeter of the spool, a shaft rotatable about the first axis, the latching gear, the cam arm and the catchment spool fixedly mounted on the shaft;
- a drive assembly having a second axis of rotation parallel to and spaced from the first axis, the drive assembly comprising, a pinion gear rotatable about the second axis and having a flange, the pinion gear engageable with the toothed portion of the latching gear, a drive means for providing a drive torque to the pinion gear, and, a leading latch cam and a trailing latch cam affixed to a face of the flange, the leading latch cam and the trailing latch cam operatively arranged to cooperatively engage the cam arm in a latched state such that counter-clockwise rotation of the cam arm and subsequent contact by the cam arm to the leading latch cam generates a counter-clockwise torque applied to the flange which increases engagement of the leading latch cam with the cam arm to further enforce the cam arm being in the latched state and such that clockwise rotation of the cam arm and subsequent contact by the cam arm to the trailing latch cam generates a clockwise torque applied to the flange which increases engagement of the trailing latch cam with the cam arm to further enforce the cam arm being in the latched state and, disengage the cam arm in an unlatched state, the latched and unlatched states selectable by operation of said drive means, the latched state preventing rotation of the shaft and the unlatched state allowing a rotation of the shaft, the pinion gear not engaging the toothed portion of the latching gear in the latched state.
2. The apparatus of claim 1 wherein the unlatched state allows a rotation of the shaft through less than 360 degrees.
3. The apparatus of claim 1 further comprising a flexible spring element, the flexible spring element engageable with the spring catchment on the catchment spool and operatively arranged to provide a latching drive torque to the rotatable assembly in the latched state.
4. The apparatus of claim 3 wherein the flexible spring element is further operatively arranged to provide a latching drive torque to the rotatable assembly in the unlatched state.
5. The apparatus of claim 1 wherein said drive means comprises one or more of an electrical motor drive, an electrical solenoid drive and a manual drive.
6. The apparatus of claim 1 further comprising a balancing weight affixed to the face of the flange, the balancing weight operatively arranged to rotationally balance the actuation assembly during operations of the drive means, thereby reducing vibrations during operation.
7. The apparatus of claim 1 wherein the leading latch cam comprises a teardrop cam and the trailing latch cam comprises an oblong cam.
8. A rotary mechanical latch for positive latching and unlatching of a rotary device, the latch comprising:
- a latchable rotatable assembly having a first axis of rotation including, a latching gear rotatable about the first axis and having a perimeter including a toothed portion and an untoothed portion, a cam arm affixed to the latching gear and rotatable about the first axis, the cam arm having an extension aligned with the untoothed portion of the latching gear, the extension having a first contacting surface and a second contacting surface, a spring catchment spool affixed to the latching gear and having a perimeter and a spring catchment disposed on the perimeter of the spool, a shaft rotatable about the first axis, the latching gear, the cam arm and the catchment spool fixedly mounted on the shaft;
- a drive assembly having a second axis of rotation parallel to and spaced from the first axis, the drive assembly comprising, a pinion gear rotatable about the second axis and having a flange, the pinion gear engageable with the toothed portion of the latching gear, a drive means for providing a drive torque to the pinion gear, and, a leading latch cam having a third contacting surface and a trailing latch cam having a fourth contacting surface, the leading latch cam and the trailing latch cam affixed to a face of the flange, the leading latch cam and the trailing latch cam operatively arranged to cooperatively engage the extension in a latched state and, disengage the extension in an unlatched state, the latched and unlatched states selectable by operation of said drive means, the latched state preventing rotation of the shaft and the unlatched state allowing a rotation of the shaft, the pinion gear not engaging the toothed portion of the latching gear in the latched state, the first contacting surface on the extension operatively arranged to produce a counter-clockwise latching torque on the flange when the extension is rotated counter-clockwise to contact the third contacting surface on the leading latch cam which increases engagement of the leading latch cam with the extension to enforce the latched state and the second contacting surface on the extension operatively arranged to produce a clockwise latching torque on the flange when the extension is rotated clockwise to contact the fourth contacting surface on the trailing latch cam which increases engagement of the trailing latch cam with the extension to enforce the latched state.
9. The apparatus of claim 8 wherein the unlatched state allows a rotation of the shaft through less than 360 degrees.
10. The apparatus of claim 8 further comprising a flexible spring element, the flexible spring element engageable with the spring catchment on the catchment spool and operatively arranged to provide a latching drive torque to the rotatable assembly in the latched state.
11. The apparatus of claim 10 wherein the flexible spring element is further operatively arranged to provide a latching drive torque to the rotatable assembly in the unlatched state.
12. The apparatus of claim 8 wherein said drive means comprises one or more of an electrical motor drive, an electrical solenoid drive and a manual drive.
13. The apparatus of claim 8 further comprising a balancing weight affixed to the face of the flange, the balancing weight operatively arranged to rotationally balance the drive assembly.
14. The apparatus of claim 8 wherein the leading latch cam comprises a teardrop cam and the trailing latch cam comprises an oblong cam.
15. The apparatus of claim 8 wherein the latched state and the unlatched state correspond to a rotation of the latching gear through a rotation angle of less than forty five degrees.
16. The apparatus of claim 15 wherein the rotation angle is approximately thirty six degrees.
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- Southco product brochure, “R4 EM Electronic Rotary Latch”, [online] [retrieved on Apr. 1, 2009] retrieved from the Internet: <URL http://www.southco.com/resources/documents/R4-EM.en.pdf.
Type: Grant
Filed: Jul 1, 2009
Date of Patent: Nov 13, 2012
Assignee: Sandia Corporation (Albuquerque, NM)
Inventors: Barry L. Spletzer (Albuquerque, NM), Michael A. Martinez (Albuquerque, NM), Lisa C. Marron (Albuquerque, NM)
Primary Examiner: Thomas Beach
Assistant Examiner: Nathan Cumar
Attorney: Olivia J. Tsai
Application Number: 12/496,413
International Classification: E05C 5/02 (20060101); E05C 5/00 (20060101); E05C 1/12 (20060101); E05C 1/06 (20060101);